Preparation of Stereocomplexed PLA Nanofibrous Membranes with High PM2.5 Filtration Efficiency
Poly(lactic acid)(PLA)nanofibers have potential applications in the field of environmentally friendly filtration materials,but their intrinsic helical molecular chains conformation and low dielectric constant result in poor electret properties,easy decay of filtration performance(e.g.,decreased filtration efficiency,elevated pressure drop),and short effective service life.The formation of highly electroactive stereocomplex crystals(SCs)was achieved by blending poly(L-lactic acid)(PLLA)and poly(D-lactic acid)(PDLA),which was promoted by facilitating the polarization of oriented C=O dipoles induced by the high-voltage electrostatic field during electrospin-ning.The existence of SCs significantly increased the dielectric constant,electret effect and surface potential of the refined PLA nanofibers.The enhanced electroactivity of PLA nanofibrous membranes(NFMs)enabled significant increase of the PM2.5 filtration efficiency to 96.32％(72.44％ for pure PLLA), while providing desirable pressure drops(85 L/min, 209.2 Pa). More importantly, the filtration performance of the electroactive PLA NFMs showed weak relation to the airflow velocity(10—85 L/min), compared to that of the pure PLLA. The excellent stability under increased airflow velocities allows great practical application potential in air filtration field. Moreover, the promotion of the electroactivity of PLA NFMs remarkably enhanced the triboelectricity and electrical signals as stimulated by respiratory vibrations, laying the theoretical foundation for human respiration-based physiological monitoring. This work reveals a new structuring strategy for expanding the application of electroactive PLA in the field of high-performance respiratory protection and intelligent physiological monitoring.
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